The present invention relates to fuel system valves, and particularly to a tank venting control assembly for regulating the flow of fuel vapor and air through a venting outlet provided in a fuel tank having a separate filler neck. More particularly, the present invention relates to a vehicle fuel vapor control valve which performs pressure-relief and vacuum-relief functions and also maintains a predetermined head pressure in the fuel tank during stationary refueling while relieving some fuel vapor pressure in the fuel tank when the vehicle is in motion.
Vehicle fuel systems are known to include tank pressure control valves configured to provide tank pressure relief and tank vacuum relief and to mount on either fuel tanks or filler necks. See, for example, U.S. Pat. No. 4,498,493 to Harris and U.S. Pat. Nos. 4,953,583 and 5,065,782 to Szlaga.
Although fuel pump nozzles are known to include sensor means for shutting off the flow of fuel from the nozzle when the fuel tank is nearly filled, it has been observed that users frequently manually override or bypass such fill-limiting sensors by continuing to pump fuel after the pump nozzle has automatically shut off several times. It will be appreciated that such unauthorized refueling practices can result in overfilling the fuel tank which can effectively reduce the fuel vapor expansion capacity available within the filled fuel tank.
It is also known to provide fuel vapor control valves for regulating tank pressure to prevent overfilling of the fuel tank during refueling. See, for example, U.S. Pat. No. 4,760,858 to Szlaga. Such a fuel vapor control valve includes a movable head valve for maintaining a head pressure within the fuel tank which exceeds the maximum head pressure that can develop in the filer neck due to filling the filler neck with fuel during refueling. Such a fuel vapor control valve aids in preventing fuel pump operators from overfilling fuel tanks by providing a pressurized fuel vapor barrier within the fuel tank that acts to block the introduction of liquid fuel into the fuel tank in excess of a predetermined fuel capacity during refueling. Such a fuel vapor control valve is adapted to vibrate and release fuel vapor during vehicle transit to increase the flow of fuel vapor to a fuel vapor treatment site and/or the atmosphere, thereby enhancing engine performance.
What is needed is a fuel vapor control valve for preventing tank overfilling during refueling and for relieving vacuum conditions that develop in a tank. Consumers would welcome a fuel vapor control valve that was also operable to vent minimal or residual tank pressure during motion of a vehicle carrying the tank and/or excessive tank pressure whether the vehicle is in motion or stationary.
According to the present invention, a fuel vapor control valve is provided for controlling the flow of fuel vapor and liquid fuel through an aperture in the fuel tank of a vehicle. The fuel vapor control valve includes a housing configured to mount in the aperture formed in the fuel tank. The housing is formed to include an inlet communicating with the fuel tank, a venting outlet, and a chamber interconnecting the tank inlet and the venting outlet in fluid communication.
A vacuum-relief valve is positioned in the chamber and is biased to a normally closed position by a spring. The vacuum-relief valve is movable to relieve subatmospheric tank pressure in response to exposure of the vacuum-relief valve to a tank pressure below a predetermined minimum tank vapor fuel pressure. The vacuum-relief valve includes a base configured to support a valve member and formed to include a venting aperture. The fuel vapor control valve further includes a ball-type head valve positioned for movement in the chamber to prevent tank overfilling when the vehicle carrying the fuel tank is stationary and to vent residual tank pressure through the chamber and the venting outlet when the vehicle is in motion.
In preferred embodiments, the fuel vapor control valve further includes a pressure-relief valve in the housing chamber in addition to the ball-type head valve. In use, the pressure-relief valve operates to vent excessive tank pressure to a fuel vapor treatment canister or other destination through the venting outlet formed in the housing. Advantageously, the ball-type head valve operates during motion of a vehicle carrying the fuel tank to vent residual tank pressure to the canister even though tank pressure does not exceed the level required to activate the pressure-relief valve. This residual pressure is normally the pressure that is left in the tank after refueling.
During refueling, the ball-type head valve closes the venting outlet to cause a pressurized fuel vapor barrier to develop within the fuel tank. This barrier acts to block the introduction of liquid fuel into the fuel tank through the filler neck once the fuel tank is filled to its rated capacity. However, once refueling is completed and this barrier is no longer needed the ball-type head valve moves in response to vehicle movement to open a vent passage in the housing chamber and vent some of the residual tank pressure through the venting outlet to the canister.
In one embodiment, the fuel vapor control valve includes a pressure-relief valve and a separate ball-type head valve is carried in a cage appended to the vacuum-relief valve. In another embodiment, the fuel vapor control valve ball-type head valve is carried in a cage appended to the vacuum-relief valve. In yet another, the fuel vapor control valve includes only a ball-type head valve carried in a cage appended to a vacuum-relief valve.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.